The present invention relates to apparatuses and methods for conveyor ovens, and, more particularly, to conveyor ovens with an extension chamber and optical sensors sensing a product in the doorway and signaling when the entrance and exit doors should rotate open, the doors operating independently.
For industrial applications servicing large numbers of food items, conveyor ovens are used instead of the conventional door oven. This has the additional advantage of not having to rely on the skill of the operator as to how long to keep the food item, for example pizza, in the oven. The baking time is determined by the length of the chamber and the speed of the conveyor.
Conventional conveyor ovens are widely used, among other things, for baking, cooking, and heating (hereinafter referred to as “baking”) of food items such as pizza. The standard oven has an inlet opening and an outlet opening and a conveyor on which the food items designated for baking are placed. The loss of heat through the inlet and outlet openings is wasteful and leads to increased energy consumption. It also creates a hot and uncomfortable work environment that leads to an additional waste of energy due to the need to air-condition the work environment.
There are approximately 100,000 conveyor ovens in the world in operation (Domino's® alone has 18,000 pizza ovens). The number one consideration in the purchase by a company of a conveyor oven nowadays is energy efficiency. It is well known that baking ovens lose heat when the food item passes through the oven since most conveyor oven sides are open for inlet and outlet. It is known in the prior art to try to solve this problem by using proximity sensors and a controller and a solenoid or motor to operate baffle mechanisms that open and close to minimize heat loss. In U.S. Patent App. Publication no. U.S. 2005/0132899 to Huang, for example, a proximity sensor 40 is used to sense the approach of the food item to the entrance door and the exit door is opened based on a calculation by the controller as to how long it will take the conveyor to carry the food item to the exit door, The controller controls a solenoid that actuates the baffle mechanism. This mechanism is not workable for its intended purpose. It cannot sense food items on all sides of the conveyor; it cannot keep track effectively of a multiplicity of food items that enter the conveyor belt in short intervals of time and space. The baffle mechanism is prone to getting stuck. It is not believed to be a reliable means of achieving significantly reduced heat loss, energy consumption, unnecessary use of air conditioning, worker discomfort, etc.
Another problem arising in these automated systems is that if the system fails, the oven doors are stuck closed and the food in the oven burns and is lost, which may be considered a catastrophe. It can also lead to a fire. Having to shut down the oven for a time until it is fixed causes further business losses.
There is a compelling need to have a conveyor oven and method that significantly reduces heat loss and energy consumption from the oven and that overcomes the drawbacks of the prior art. It would be particularly helpful if such an apparatus or method would prevent catastrophe, would make the worker environment for industrial conveyor ovens more bearable in terms of temperature, and would save on use of air conditioning.